Liner support disc for supporting friction liners, especially for a motor vehicle

ABSTRACT

A liner support disc for supporting friction liners, adapted to constitute a clutch friction wheel, especially for a motor vehicle, of the kind comprising a central portion and a peripheral portion divided into radial blades for receiving the friction liners, with each of the blades being joined integrally to the central portion through a foot, and comprising at least one support zone which is generally parallel to the mean plane of the central portion, for contact with at least one of the friction liners and for fastening of the latter. In a clutch friction wheel, the liners lie on either side of the peripheral portion.

BACKGROUND OF THE INVENTION

a) Field of the Invention

The present invention relates to a liner support disc for supportingfriction liners, adapted to constitute a clutch friction wheel,especially for a motor vehicle, of the kind comprising a central portionand a peripheral portion divided into radial blades for receiving thefriction liners, with each of the said blades being joined integrally tothe said central portion through a foot, and comprising at least onesupport zone which is generally parallel to the mean plane of the saidcentral portion, for contact with at least one of the said frictionliners and for fastening of the latter. In a clutch friction wheel, thesaid liners lie on either side of the peripheral portion.

b) Description of Related Art

Clutch friction wheels are sometimes subject in operation todisagreeable vibrations constituting what is often called judder. Thisjudder is just as likely to occur at low torques, during a parkingmanoeuvre, as at high torques during a gear change when travelling, andduring a hill start.

The support zones are sometimes not as large as desired, which givesrise to an embedding effect in which the friction liners become embeddedin the hollows that exist between two support surfaces of the sameblade.

This gives rise to a lack of flexibility, which is at least partlyresponsible for judder effects at maximum load.

In addition, there is a problem of contact with, in particular, thepressure plate of the clutch.

In this connection, in a clutch, each time the clutch is engaged, thefriction liners become progressively gripped between a pressure plateand a reaction plate.

The heating which is caused by the friction leads inevitably todeformation of the pressure plate into a conical form, as is explainedfor example in the document U.S. Pat. No. 2,902,130, while the same istrue, though to a lesser extent, for the reaction plate.

As a result, the zone in which the friction liners are subjected to thepressure from one or other of these plates becomes progressively offsettowards the axis of the assembly, with consequent unequal wear of thesaid friction liners and a reduction in their efficiency (i.e. reducedtorque transmission), and even the occurrence of judder effect.

In order to overcome these drawbacks and to resolve this problem, it hasbeen proposed in the document EP-A-0 579 554 to provide blades of thetripod type which have a central support zone and two peripheral supportzones on either side of the said central zone, which is offset axiallywith respect to the peripheral support zones and the central portion.

In one embodiment, the said blades are in circumferential alternationwith a series of tongues.

In another embodiment, the said blades are arranged in circumferentialalternation with a second series of blades of the tripod type, in theimage of the first series.

The tripod blades serve for the fastening, in their central zone, of oneof the friction liners, in this case the one which is associated withthe pressure plate of the clutch, while the tongues serve for thefastening of the other friction liner, in this case the one that isassociated with the reaction plate of the clutch.

By virtue of this arrangement, the tongues, or the tripod blades of thesecond series, have sufficient elasticity to follow the tendency of thereaction plate to adopt a conical form, while the tripod blades followthe tendency of the pressure plate to adopt a conical form, and havelarge contact surfaces.

In addition, embedding and judder effects are reduced, and the bladesare able to rotate at higher speeds, which eliminates bending forces inthe blade feet caused by centrifugal force.

In the said document, fastening of the friction liners is achieved bymeans of a row of rivets arranged on a common pitch circle. As a result,the central zone of the first series of tripod blades is provided withan aperture for passage through it of a rivet which constitutes afastening member.

The same is true of the tongues or of the central zone of the secondseries of tripod blades.

For clutch friction wheels of large size (large diameter), or when thefriction liners are thin, being adhesively secured on foils which arecarried by riveting on the liner support disc, it is then necessary toprovide at least two rows of rivets arranged on pitch circles ofdifferent diameters.

A problem of locating the holes for accommodating the fastening membersthen arises in connection with the central zone of the tripod blades,because it is necessary to space the holes which accommodate the rivetsby a substantial radial distance apart for proper fastening of thefriction liners, and therefore to increase the radial depth of thecentral zone.

Similarly, when it is desired to secure the liners adhesively on thecentral zones, it is desirable to increase the radial size of thecentral zones in order to support the friction liner internally andimprove the strength of adhesion.

SUMMARY OF THE INVENTION

An object of the present invention is to respond to these requirements,and accordingly to provide, in a simple and inexpensive way, noveltripod blades which enable the radial size of the central zones to beincreased.

With the central zone of a tripod blade being joined to the centralportion of the liner support disc, by means of a foot which includes atleast one inclined zone in the form of a longitudinal bent portion atright angles to the radial axis of symmetry of the tripod blade,according to the invention the central zone of at least some of thetripod blades is extended radially inwardly by virtue of a slot formedacross the said longitudinal bent portion.

Due to the invention, in all cases the engagement surface for the linerconcerned, and therefore the resistance of the liner support disc tocentrifugal force, are increased. It is possible to arrange in the sameplane at least two fastening holes spaced apart radially from eachother, in the central zone of one tripod blade.

In this connection, it is enough to provide the extension in accordancewith the invention with an additional hole for passage through it of afastening member for the friction liner. This flexible extension alsoreduces the chance of rupture.

Thus it is possible to secure the friction liner concerned (which may beof divided form) to the central zones of the first series of tripodblades, by means of at least two sets of rivets or other fasteningmembers, spaced apart radially from each other.

The friction liner is thus well secured. This liner may then rotate athigh speeds of rotation.

Similarly, it is possible to secure the friction liner directly byadhesive bonding on the central zones.

In this connection, because of the extension, the said liner is securedlocally over an increased depth, which is favourable to good adhesion.In addition, the damage of peeling or separation is reduced because ofthe flexible extension.

It is of course possible to retain the hole of the prior art, and tosecure the liner adhesively or by riveting.

Nevertheless, it will be appreciated that the arrangement having onlyadhesive bonding is advantageous because it enables the thickness of thefriction liners to be reduced to a useful value. In this connection,there is no need to provide any extra thickness as in a rivetedarrangement. The inertia of the clutch friction wheel is thus reduced.The mechanical strength of the central zones is increased due to thefact that there is no need to provide a rivet hole. The friction wheelis therefore able to rotate at even higher speeds of rotation.

It will be appreciated that the arrangement in accordance with theinvention is inexpensive, because it does not render necessary anysubstantial modification of the manufacturing tooling for the linersupport disc.

In this connection, it is enough to form the slot by press forming witha simple tool and to provide, or not, two rows of fastening holes. Inaddition, the extension in accordance with the invention increases thesupport zone of the liner concerned without any detriment to themechanical strength of the longitudinal bent portion.

In accordance with another feature, in order to preserve the maximumamount of support for the friction liner concerned, with distancesbetween engagement surfaces being as small as possible, the number ofblades is multiplied.

As a result, these blades have a reduced circumferential width, and itis then possible to configure the above mentioned tongues, which aregenerally in the plane of the central portion, as tripod blades with acentral zone in the plane of the central portion, together with twoperipheral support zones on either side of the said central zone.

Thus, during the elastic compression of the friction liners, thefriction liner which is associated with the tongues undergoes a reactiondue to new peripheral support zones, which are adapted to makeengagement against the other friction liner.

Embedding effects are thus reduced, with wear in the friction linerassociated with the tongues being better distributed. In addition, weareffects in the friction liner associated with the first set of blades isreduced because the peripheral support zones of the tongues provide anadditional engagement surface. For the other friction liner, wear ismade more even.

It is of course possible to replace the above mentioned tongues with asecond set of tripod blades.

In a modification, at least some of the said tongues have, in a bentjunction portion, at least one additional support zone which is offsetaxially towards the central zones of the first set of tripod blades.

The supplementary zones may be situated at the free end of the tongue orwithin the latter, being defined by a slot. Any combination is possible.

As before, embedding effects are reduced, while wear in the frictionliner associated with the tongues is more evenly distributed because ofthe additional support zone.

According to one feature, the slot is formed locally in the central zoneof the tripod blade, in order to reduce the risk of rupture in theregion of the extension.

BRIEF DESCRIPTION OF THE DRAWINGS

The following description illustrates the invention with reference tothe attached drawings, in which:

FIG. 1 is a view in axial cross section of a clutch friction wheelequipped with a liner support disc in accordance with the invention;

FIG. 2 is a partial view in elevation of the said liner support disc,with the support zones shown cross hatched;

FIGS. 3 to 10 are views similar to FIG. 2 for further embodiments;

FIG. 11 is a view in cross section taken on the line 11--11 in FIG. 10.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The drawings show a liner support disc which is adapted to form part ofa clutch friction wheel for a motor vehicle.

This friction wheel (FIGS. 1 and 2) comprises a central portion 16 and aperipheral portion which is divided into radial blades 771 which arearranged alternately in the circumferential direction, being in thisexample at regular intervals, with a series of radial tongues 772 in theplane of the central portion 16 of the liner support disc. In theseFigures, the blades 771 and tongues 772 are integral with the centralportion 16.

As is described in the Application EP-A-0 579 554, each blade is joinedto the central portion 16 through a longitudinal foot 724, and has acentral support zone 722 and two peripheral support zones 723 at itsouter periphery.

The wide central zone 722 is offset axially with respect to the centralportion and with respect to the peripheral support zones 723.

The central zone 722, which is large, serves for the fastening of afriction liner 132, while the tongues 772 serve for the fastening of afurther friction liner 131. To this end, the tongues 772 and the centralzones 722 of the blades 771 are formed in this example with holes 19,for the fastening of the said liners 131, 132 to the liner support disc,in this example by means of rivets 47 (FIG. 1).

In accordance with one feature of the invention, the holes 19 aredistributed over two pitch circles of different diameters. In amodification, some of the holes 19 do not lie on the said pitch circle,so that they define a zig-zag. In a modification, adhesive fastening maybe used, which enables the fastening holes to be omitted, and thestrength of the blades to be improved, in a manner described below.

The liner support disc is equipped with two annular friction liners 131,132 which are mounted in back-to-back relationship on either side of thecentral portion 16.

These friction liners are in this example of the organic type, beingcircumferentially continuous and reinforced by glass fibres of KEVLAR,or otherwise.

In a clutch, the liners 131, 132 are normally gripped between thepressure and reaction plates (not shown) of the clutch, which are fixedto the crankshaft of the internal combustion engine of the motor vehiclefor rotation with it, while the hub 3 is coupled, through its splinedinternal bore, to the input shaft of the gearbox for rotation with thelatter.

During operation of the clutch to disengage the latter, the frictionliners 131, 132 are released so that in the disengaged position of theclutch, the liners are not in contact with the said pressure andreaction plates.

When the clutch is re-engaged, the liners 131, 132 are grippedprogressively and elastically between the said plates.

This progressive gripping action is due in the present case mainly tothe tripod blades 771, and more particularly, it is due to theirperipheral support zones 723 and the foot 724.

The said blades 771 are of tripod form, with three flat support orengagement zones, 723 and 722 respectively.

The flat central zone 722 is in contact with the friction liner 132which is associated with the pressure plate, and serves for thefastening of the said liner 132. This zone 722 reduces in width towardsthe outer periphery of the liner support disc. It is thus wider at itsinner periphery.

More precisely, the liner support disc with its liners 131, 132 is inthis example part of a clutch friction wheel which comprises two coaxialparts mounted for movement of one with respect to the other against theaction of circumferentially acting resilient means 5 and axially actingfriction means 20.

Such a friction wheel is described, for example, in the ApplicationEP-A-0 579 554, and in U.S. Pat. No. 5,014,842, to which reference canbe made.

In the present example, one of the parts comprises two guide rings 1, 2together with the liner support disc, while the other coaxial partcomprises a damper plate 4 which is secured by seaming (not shown) to ahub 3 for rotation with the latter, or, in the present case, by means ofloose coupling means which can be seen in particular in FIG. 3 of U.S.Pat. No. 5,014,842.

Accordingly, these means comprise trapezoidal teeth which are formed onthe outer periphery of the hub 3 and on the inner periphery of thedamper plate 4, with the said teeth meshing together and having aclearance between them.

Low stiffness springs, not shown, engage at each of their ends on cupmembers which are fitted in slots of the hub 3 and damper plate 4, so asto give elastic coupling between the said components.

It is possible to reverse the structures, with the liner support discthen being secured to the damper plate 4 which is movable in rotationwith respect to the hub 3, while the guide rings are then fixed to thehub 3.

Similarly, the liner support disc may be fixed to the damper plate 4,which is itself secured to the hub 3, the clutch friction wheel thenbeing of the rigid type as can be seen in the document EP-A-0 579 554.

In this example, the liner support disc is abutted in its centralportion 16 to the guide ring 1, and is secured to the latter by means ofspacers which extend, with a clearance, through apertures 7 formed inthe damper plate 4.

These spacers 8 secure together the guide rings 1, 2 which are arrangedon either side of the damper plate 4.

The resilient means 5 consist in this example of coil springs which arehere mounted in pairs, in windows formed in facing relationship witheach other in the guide rings 1, 2 and in the damper plate 4 in a mannerknown per se.

The friction means 20 comprise a friction ring which is interposedaxially between the damper plate 4 and the ring 1, together with athrust ring which is mounted on the guide ring 2, for rotation with thelatter, by means of axial lugs which are engaged in apertures formed inthe said ring 2.

A spring bears on the ring 2, and biasses the thrust ring into contactwith the damper plate 4.

The zones 723 lie at the outer periphery of the blades 771, on eitherside of the central zone 722. They are generally triangular in shape andare joined to the zone 722 through bent portions 721, which are obliquewith respect to the radial axis of symmetry of the blade 771. These bentportions 721 are axially inclined, and lie symmetrically with respect tothe said radial axis.

The zones 723 and 722 are thus offset axially because of the axiallyoffset bent portions 721, while being parallel to each other. Moreprecisely, the zones 723 are arranged to make contact with the frictionliner 131 associated with the reaction plate of the clutch. In thepresent example they extend in the plane of the central portion 16.

The central zone 722 is joined to the central portion 16 through atangentially orientated bent portion 724, or longitudinal bent portion,which in this example is at right angles to the radial axis of symmetryof the blade. This axially oblique bent portion 724 constitutes the footof the blade, and gives an axial offset of the zone 722 with respect tothe central portion 16. The bent portion 724 extends, here,symmetrically with respect to the said radial axis.

Thus, when the liners 131, 132 are compressed, the zones 723 deformaxially. It will be noted that the bent portions 724 are of large widthand therefore very robust. Vertical slots 224 separate the blades 771from the tongues 772. These slots are open at the outer periphery of theliner support disc, and have a circular closed inner end for theirjunction with the bent portions 724 and central portion 16.

The cranked blades 771 are of reduced circumferential extent as comparedwith that in the document EP-A-0 579 554, so that the tongues 772 have acircumferential width which is close to that of the blades 771 inaccordance with one feature of the invention. The engagement surfacesfor each liner are thus as close as possible to each other.

This is done with a view to preserving the maximum engagement surfacearea for the friction liners 131, 132, with the smallest possibledistances between engagement, surfaces.

The number of blades is thus multiplied. In this example, the clutchfriction wheel being of large size, the arrangement involves, forexample, fitting at least two rows of fastening members 47, such as theabove mentioned rivets, or screws or bolts, in order to secure thefriction liners 131, 132 and therefore to provide at least some blades771 with at least two fastening holes 19 for passage through them of thesaid fastening members.

In a modification, it is possible to provide a single row of rivetstogether with adhesive fastening, or adhesive fastening by itself. Inevery case the clutch friction wheel must have improved resistance tothe effects of centrifugal force.

Thus, in accordance with the invention, a liner support disc of the typedescribed above is characterised in that the central zone 722 of atleast some of the tripod blades 771 is extended centrally (at 725)radially inwardly by virtue of a slot 726 formed in the longitudinalbent portion 724. In FIGS. 1 and 2, the said extension 725 is providedwith an additional hole 19 for passage through it of a fastening member47, which in this example is a rivet 47. The engagement surface for theliner 132 is thus increased, and the fastening of the liner 132 isstronger.

As can be seen in FIG. 2, a further fastening hole 19 is arranged at theouter periphery of the central zone 722 and blade 771.

Thus the holes 19 for fastening of the liner 132, lying in the sameplane, are separated from each other radially by a substantial distance,and in this example they are arranged radially on the axis of symmetryof the blade 771.

According to one feature, the tongues 772 are in the image of the blades771, and accordingly, in this example, they have a central zone 823 inthe plane of the central portion 16, together with two peripheralsupport zones 822 on either side of the said central zone 823.

A bent portion 821, which is oblique in the axial direction and inclinedin the radial direction, joins each zone 822 to the peripheral portionof the central zone 823. The zones 822 are offset axially towards thecentral zones 722 of the blades 771. They may be in the same plane asthe latter, or slightly behind it in the axial direction.

Two fastening holes 19 in a common plane are provided in the centralzone 823. These holes 19 are radially aligned on the radial axis ofsymmetry of the tongue 772, being located on the same pitch circles asthe holes 19 of the blades 771.

In some of the tongues 772, these holes are aligned with a fasteninghole 119 for securing the central portion 16, by riveting in FIG. 1, tothe damper plate 4, which is itself secured by riveting on a flange ofthe hub 3.

In a modification, indicated in broken lines in FIG. 2, the tongues 772could of course be replaced by a second set of cranked tripod blades, ofsimilar form to the blades 771, with a longitudinal bent portion joiningthe central zone to the central portion 16 of the liner support disc.

In this example, the slot 726 in accordance with the invention isV-shaped with a rounded base, with the point of the V being directedtowards the axis of the friction wheel (i.e. towards the axis of thecentral portion 16). The extension 725 thus has the form of a rounded V.It constitutes an additional engagement lug oriented generally radiallyinwardly, as in the other Figures described below.

This slot is formed in the bent portion 724, and locally in a small partof the central zone 722 and the central portion 16. The bent portion 724is thus divided into two, which improves the above mentioned progressivegripping effect. The bent portion 724 has good mechanical strength inspite of the slot provided in accordance with the invention.

It will be noted that the extension 725 has a divergent root zone bywhich it is joined to the central zone 722.

Risks of rupture are reduced because of this root zone.

The radial axis of symmetry of the slot 726 is coincident with theradial axis of symmetry of the blade 771.

It will be appreciated that the good equilibrium of the clutch frictionwheel, and good flatness of its friction liners, are due in particularto the regular spacing of the fastening holes 19 and to their positionon the axis of symmetry of the tongues 772 and blades 771.

The simplicity of manufacture of this arrangement will also be noted,this being due to the radial displacement of the press tool that can beobtained, enabling discs to be made with blades and tongues of differentdepths.

In this example, in the position in which the clutch is engaged (withthe liners 131, 132 gripped), a space exists between the two liners 131,132 so that the blades 771 are not totally squeezed, and so that thesaid liners are permitted to adapt to the form of the pressure andreaction plates.

The tripod blades may of course have another shape, such as thatdescribed in the above mentioned document EP-A-0 579 554.

Thus in FIG. 3, the tripod blade 971 has a central support zone 922which is of reduced width at its outer periphery, and which is offsetaxially with respect to the central portion 16, by virtue of the bentportions 921, oblique with respect to the radial axis of symmetry of theblade, and the longitudinal bent portion 924 at right angles to the saidaxis of symmetry.

The central zone 922, as in FIG. 2, is extended radially inwardly in themiddle, by a U-shaped central slot 926 which is formed in thelongitudinal bent portion 924. This extension is generally in the formof a tongue or lugs 925, having a root zone that joins it to the centralzone 922 of reduced width, with the vertical ends of the slot 926 beingopen into circular holes formed in the zone 922 having the slot 926.

The lug 925 is thus directed towards the axis of the assembly, and has arounded free end.

The peripheral support zones 923 are generally in the plane of theportion 16. These zones 923 project circumferentially with respect tothe central zone 922, in such a way that the blades 971 are generallyT-shaped.

Advantage is taken of this shape to increase the circumferential widthof the tongues 972, 973 in their middle radial zone. Thus, these tongues972, 973 are, in their radially central part, wider than at their freeends and wider than in the zone by which they are joined to the portion16.

In this example, the radial tongues 972 and 973 are of differentconfigurations. These tongues are arranged in regular alternation in thecircumferential direction with the blades 971. The free end of thetongue 972 is of reduced circumferential width, and has a supplementarysupport zone 942 joined to the main portion of the tongue through aconnecting bent portion 941, which for good flexibility has a constantwidth at the level of the zone 942, offset axially towards the centralzone of the support surface 922 of the blades 971. This bent portion 941is widened at its base. In this example, the supplementary zone 942 isin the plane of the zone 922 of the blade 971. The said zone 942 can ofcourse be situated slightly further back with respect to the zone 922.

The tongue 973 has at its free end a zone 932, which is joined through abent portion 931 to the main zone of the tongue 973.

The bent portion 931 and the zone 932, which are here in the plane ofthe central zone 922, are trapezoidal in shape.

As will have been understood, because of the two sets of tongues, it ispossible to provide an axial offset between the zones 942 and the zone932, in such a way that the liners are well supported during engagementof the clutch.

In this example, the central portion 16 has fastening holes 119 for thefastening of the central portion 16 to the guide ring 1, or to thedamper plate 4 as the case may be.

It will be noted that the slot 926 is formed centrally in the bentportion 924, which is thus divided into two, and this improves theprogressive gripping of the blade 971. This bent portion has goodmechanical strength in spite of the slot.

It will be noted that the slots 324 that separate the radial tongues972, 973 from the blades 971 have a non-straight shape due to thecentral widening of the said tongues.

In this example, the liners 131 and 132 are secured directly by adhesionon the main part of the tongues 972, 973 and on the central zones 922 ofthe blades 971. It will be noted that the flexible extension 925 isfavourable to adhesive bonding.

By virtue of all these arrangements, it is possible to reduce thethickness of the liners 131, 132.

Thus, the said liners 131, 132 have just the required thickness, becausethere is no need to provide any thickened portion for the rivets 47 asin the embodiment of FIGS. 1 and 2.

Thus the inertia of the clutch friction wheel is reduced, which isbeneficial to conservation, during disengagement of the clutch, of thegears of the gearbox on the input shaft of which the hub 3 is mounted.

In addition, the blades and the tongues are stiffened because they donot have holes for accommodating rivets.

Accordingly, it is possible to benefit from this so as to create, forexample in the tongue 972, a supplementary support zone 944 which isoffset axially towards the zone 922 by virtue of a bent portion 945which joins the said zone 944 to the main part of the tongue 972 in theplane of the portion 16.

The provision of this supplementary zone is obtained by virtue of a slot946, which is generally V-shaped and which is directed radially inwardlyby contrast with the slot 926.

Thus, a tongue or lug 944, 945 is formed which is directed radiallyoutwardly, extending symmetrically with respect to the radial axis ofsymmetry of the tongue 972.

The provision of the supplementary support zone 925 does of course alsoenable a supplementary hole to be provided for the fastening of theliner 132 by riveting, as in FIG. 2.

Thus, in FIG. 4, each tongue 1072 and each tripod blade 1071 has twoholes 19, through which pass the fastening members for the liners 131,132.

These holes are radially aligned on the radial axis of symmetry of theradial tongues 1072 and blades 1071.

One of the holes 19 is located in the zone of the extension 1025 of thecentral zone delimited by a U-shaped slot 1026, which is formedcentrally in the longitudinal bent portion 1024 of the blade 1071. Theextension 1025, in the form of a tongue or lug, is in the plane of thecentral support zone 1022 of the blade 1071, with the zone 1022 beingoffset axially with respect to the central zone 16, by virtue of thebent portion 1024 and the bent portions 1021 which are oblique withrespect to the radial axis of symmetry of the blade 1071.

The bent portions 1021 are joined to the peripheral support zones 1023which are generally parallel to the bent portions 1021.

The zones 1023 are generally in the plane of the zone 16.

The shape of the tongues 1072 is generally similar to that of the blades1071, the only difference being that their main part is in the sameplane as the central zone 16.

The radial tongues 1072 thus have at their outer periphery twosupplementary peripheral support zones 1122, which lie generally in thesame plane as the central zone 1022 of the blades 1071.

These zones 1122 are joined to the main zone of the said tongue throughbent portions 1121, which are oblique with respect to the radial axis ofsymmetry of the tongue 1072.

In this embodiment, the blades 1071 are widened at their outerperiphery, and the tongues 1072 are widened circumferentially at theirouter periphery.

The tongues and the tripod blades can of course be separate from eachother, being attached, for example by holes 229, to the guide ring 1 ordamper plate 4.

Thus in FIG. 5, the tripod blades 772 are in circumferential alternationwith the radial tongues 771, having a shape similar to that of theblades 772 as shown in FIG. 2.

In this way, the inner periphery 316 of the tongue 771 has two holes 229through which fastening members such as rivets pass for securing to theguide ring 1 for example.

In this embodiment, the tongue 771 has a supplementary support zone 1125in its central part.

This zone 1125 is in the same plane as the central zone of the blade772, and is joined through a bent portion 1124 to the main portion 1128of the tongue 771.

All of this is obtained by virtue of the slot 1126 which is generallyV-shaped.

The bent portion 1124 with the tapered support zone 1125 generallyconstitutes a tongue or lug which is directed towards the axis of theassembly, by contrast with the embodiment of FIG. 3.

The tongue 772 is extended radially beyond its longitudinal bentportion, towards the axis of the assembly, so that it can be fastened tothe guide ring, with the aid of holes 229 through which fasteningmembers pass.

With reference to FIG. 6, the tongue 771 and blade 772 can of course bejoined together at their base.

In that case, each blade 771 is integral with an integral strip 116,which is generally in the form of an angular sector.

The strip 116 joins one blade 771 to one tongue 772, and has threefastening holes 229 for securing it to the guide ring 1 or damper plate4, in this case by riveting.

In FIGS. 5 and 6, the blades 772 and the tongues 771 are mirror imagesof each other, since their central zone has a generally V-shaped lug1025, 1124, 1125 directed towards the axis of the assembly.

The lug 1025 is formed in the longitudinal bent portion of the tongue772 as explained above. The liners 131, 132 can be secured by adhesivebonding and riveting (with the aid of the holes 19), since the lug 1025permits such adhesive bonding.

It is of course possible (FIG. 7) to divide the central portion intostrips 226 with ears at each of their circumferential ends. The ears areprovided with holes 229, and overlap as between a tongue and aconsecutive blade 772.

The strips 226 are secured in this embodiment to the guide ring 1, byriveting through the holes 229.

The blades 771 and the tongues 772 may of course (FIG. 8) be integral asin FIG. 2, with the holes 19 for the blades 772 being arranged as inFIGS. 5 to 7 on a pitch circle of a different (smaller) diameter fromthat on which the holes 19 associated with the tongues 771 are arranged,the holes 119 being formed in tongues.

As in FIGS. 5 to 7, it is of course possible to secured the liners byadhesive bonding and by riveting, with the adhesive bonding replacingthe second set of rivets. The tongues 771 may consist of tripod bladeswith a lug 1025.

In FIG. 9, the liner support disc includes two attached support discs,each of which comprises blades of the tripod type. These blades have aform similar to that ill FIG. 6, and accordingly each of them is securedon the appropriate support disc by means of the holes 229.

These support discs are attached, and are secured to each other by meansof the spacers 8 in FIG. 1, at the same time as the guide ring 1.

The tripod blades 771 are thus arranged alternately with tongues 772,being separated by slots 524, 224. The tripod blades are mounted back toback, with the friction liner 131, 132 being secured adhesively to thecentral zones of the tripod blades 771.

Thus, one of the friction liners is secured adhesively on the centralsupport zones of one of the sets of tripod blades, while the other lineris secured adhesively on the central zones of the other set of tripodblades.

Coupling means 501, 502, having a uni-directional axial action and beingadapted to limit the axial spacing between the two support discs, arearranged between these latter.

The said spacing means are fitted at the level of some of the centralsupport zones of the tripod blades 771.

Thus, in this example, there is a regular alternate arrangement oftripod blades 771, similar to those in FIG. 2, and tripod blades havingcoupling means. These coupling means comprise hooks 501, 502. The hookscomprise a lug 501, 502 which extends longitudinally parallel to thecentral support zone of the appropriate support disc.

The lug 501, 502 is joined to the central support zone through a bentportion 510. The lugs are defined in a pressed-out portion 500 in theform of an oblong hole formed in the central support zone.

Thus the hook carried by one of the discs is arranged to come intoabutment with an associated abutment surface which is carried by theother disc. This other disc carries a lug 502 in the image of the lug501.

In this way, a hook 501, 502, 510 is provided, which extends mainly onone side of the radial axis of symmetry of the tripod blade, and onlythe lug 501, 502 lies on either side of the said axis in order tocooperate with the associated lug of the other disc.

Thus, the lug 501, 502 extends parallel to the central support zone,being offset axially towards the friction liner opposite to that whichis secured on the central zone of the appropriate tripod blade.

As will be understood, one of the discs includes at least one lug 501,502 extending from one edge of the central support zone towards theother edge of the said central support zone, and vice versa for theother disc.

It is thus possible to provide a bayonet fitting. For example, the lug501 of one of the discs is introduced into the aperture 500 of the otherdisc, and is then rotated circumferentially so as to make engagementwith the associated lug 502 of the other disc.

The aperture 500 is of course dimensioned accordingly.

A sub-assembly is thus easily made up, comprising the two discs withtheir blades 771 and tongues 772 and the liners 131, 132, with the axialspacing being limited by cooperation of the lugs 501, 502.

This sub-assembly is then fitted on the guide rings 1, 2 by means of thespacers 8.

The lugs 501, 502 are in engagement with each other when the clutch isdisengaged, and the axial spacing between the tripod blades is thuslimited.

The lugs 501, 502 are generally, when the clutch is disengaged, in thesame plane as the peripheral support zones of the tripod blades, whichare themselves generally in the same plane as the discs.

It will be appreciated that the friction liners 131, 132 are adhesivelysecured over a large surface area.

It is of course possible (FIGS. 10 and 11) to provide supplementarysupport zones 1425 in the blades 1471, in the peripheral support zonesof the said blade.

The support zones 1425 extend in the same plane as the central zone1422. More precisely, the central zone 1422 is joined through an obliquebent portion 1421 to a peripheral support zone 1423 in the same plane asthe main portion of the tongue 1472.

This zone 1423 is joined through a bent portion 1424, which is obliquewith respect to the radial axis of symmetry of the blade 1471, to thesupplementary support zone 1425. The said zone 1425 is in the same planeas the supplementary zone 622 of the tongue 1472. The zone 622 isdefined at the free end of the tongue 1472, and is generally rectangularin shape. It is joined to the main portion of the tongue 1472 through abent portion 621, which is similar to the bent portions 941 and 931 inFIG. 3.

This tongue 1472 also has, as in FIGS. 5 to 8, a supplementary supportzone 1125 which is joined through a bent portion 1124 to the mainportion of the tongue 671.

All of this is defined by a generally V-shaped slot 1426. Thus the zone1125 is in the same plane as the central zone 1422.

By virtue of all of these supplementary zones, which define zones ofstabilisation, good stability is obtained for the friction liners, andthis is favourable to a reduction in wear. The said liners are wellsupported.

It is of course possible to secure the friction liners 131, 132adhesively to the tongues and blades 771, 772.

The present invention is of course not limited to the embodimentdescribed.

The friction liners 131, 132 may be of divided form. In a modification,each liner may include a continuous support crown in which openings areformed for securing friction pads in the manner described in the abovementioned document EP-A-0 579 554.

The feet of the blades may be constituted not only by the tangentialbent portions, so that an end portion of the feet joins the bentportions to the central portion of the friction wheel.

According to the particular application, it is of course possible toomit the support zones formed at the outer periphery of the radialtongues. For example in FIG. 5, it is possible to omit the bent portion941 and the zone 942, and to retain the zone 944 and the slot 946.

It is also possible to provide two pressed-out openings directed inopposite radial directions and bounding a connecting bent portion thatcarries a supplementary support zone.

All combinations are possible.

It will be appreciated that in FIGS. 5 to 8, the three supplementarysupport zones, namely the portion 1125 and the two peripheral supportzones of the tongue 771, are carefully spaced apart in a triangularmanner which is highly favourable to the stability and reduction in wearof the liners 131, 132.

The oblique bent portions that join the peripheral support zones to thecentral zone may of course be arranged asymmetrically with respect tothe radial axis of symmetry of the blade. The same is true for thecentral zone.

The supplementary support zones are not necessarily arranged on theradial axis of symmetry of the tongue. A slight offset can exist.

In general terms, it will be noted that in FIGS. 3 to 8 and 10 to 11,the tongues offer at least one additional support zone.

Thus, during compression of the liners 131, 132, the respective zone orzones 932-822-1122 are adapted to make contact with the liner 132 so asthus to offer a reaction surface. The said zones accordingly constitutestabilising zones which, in this example, extend in the plane of thecentral zone 722 by virtue of the above mentioned bent portions931-821-1131.

In a modification, these zones may be slightly retracted with respect tothe central zones. Thus the liner 131 remains very flat.

In this way, a liner support disc is obtained which has large supportzones at its outer periphery, reducing embedding and judder effectsbecause the friction liners 131, 132 remain in a substantially parallelplane. The liner support disc, and therefore the friction wheel, canthus rotate at high speeds while following the tendency of the pressureand reaction plates to adopt a conical configuration. The distributionof wear in the liners is improved even more.

It will be appreciated that the bent portions724-924-1024-931-921-821-1121-1021 give good stability to the linersupport disc, which enables good contact to be obtained between thefriction liners and the pressure and reaction plates, which reduces wearin the friction liners.

It will be appreciated that good balancing of the friction wheel, andgood flatness of its friction liners, are due in particular to theregular distribution of the fastening holes 19, and to their position onthe axis of symmetry of the tongues and tripod blades.

In this example, in the clutch engaged position (with the liners 131,132 in a gripped condition), a space exists between the two liners 131,132 such that the blades are not totally compressed, so as to enable thesaid liners to adapt to the shape of the pressure and reaction plates.

In FIGS. 10 and 11 it will be noted that the central support zone 1422has at its inner periphery two lugs which are arranged on either side ofthe longitudinal bent portion 1024. These lugs enable the supportsurface of the zone 1422 to be increased in association with the lug1025.

It is thus possible to secure the friction liner 132 adhesively on thesaid zone 1422.

In all cases the flexible extensions, which are generally in the form oflugs 725-925-1025, in accordance with the invention enable theappropriate friction liner to be secured adhesively.

The said flexible lugs are accordingly coated with adhesive.

We claim:
 1. A liner support disc for a clutch friction wheel comprisingat least one central portion (16) and a peripheral portion divided intoat least one series of radial blades (771-971-1071-1471) of tripod type,in which said blades have, defined by bent portions (721-921-1121-1421),a central support zone (722-922-1022-1422) and two peripheral supportzones (723-923-1023-1423) on either side of said central zone, saidperipheral zones being offset axially with respect to said central zone,and in which said central support zone is joined to the at least onecentral portion (16) through a foot which includes an inclined zone inthe form of a longitudinal bent portion (724-924-1024) at right anglesto the radial axis of symmetry of a said blade, characterized in thatthe central zone (722-922-1022-1422) of at least some of the tripodblades (771-971-1071-1471) is extended centrally (at 725-925-1025)radially inwardly by virtue of a slot (726-926-1026) formed in thelongitudinal bent portion (724-924-1024).
 2. A liner support discaccording to claim 1, characterized in that said extensions(725-925-1025) are in the form of lugs extending generally radially. 3.A liner support disc according to claim 1, characterized in that theslots (726-926-1026) define said central zone (722-922-1022-1422)locally.
 4. A liner support disc according to claim 3, characterized inthat the slots (726) are generally V-shaped with a rounded base, withthe point of the V being directed towards the axis of the centralportion (16).
 5. A liner support disc according to claim 3,characterized in that the slots (926-1026) are U-shaped, with the basethereof being directed towards the axis of the central portion (16). 6.A liner support disc according to claim 5, characterized in that theextension (925) is U-shaped, with a root zone of reduced width joiningit to said central zone.
 7. A liner support disc according to claim 1,characterized in that the radial axis of symmetry of the slots(726-926-1026) is coincident with the radial axis of symmetry of thetripod blades (771-971-1071-1471).
 8. A liner support disc according toclaim 1, characterized in that the tripod blades (771-1071) are arrangedin circumferential alternation with tongues (772-1072) in image of saidblades, so that the said tongues have a central zone (823-1023) in theplane of the central portion (16), together with two peripheral supportzones (822-1122) on either side of said central zone (823-1023).
 9. Aliner support disc according to claim 1, characterized in that saidtripod blades are arranged in circumferential alternation with tongues(972-973-1472) having, in a bent junction portion (931-941-621), asupport zone (932-942-944-1125) which is offset axially towards saidcentral zones of the associated tripod blades (971-1471).
 10. A linersupport disc according to claim 1, in which said central support zone ofthe tripod blades (771-1071) has at least one hole (19) for the passageof a fastening member (47) through it, characterized in that saidextension (725-925-1025) is provided with an additional hole (19) forthe passage of a fastening member through it.
 11. A liner support discaccording to claim 1, characterized in that said extension(725-925-1025) is coated with adhesive.